The present invention relates to an ink jet printing apparatus comprising means for automatically sensing and removing an ink clog.
Although ink jet printers offer many advantages, the ink ejection nozzles thereof are prone to ink clogs. Various proposals have been made to automatically sense and clear ink clogs but none of these have proven entirely effective.
One prior art arrangement which is applicable to a deflection type system is to increase the ink pressure while vibrating the nozzle with a vibrator. Another proposal which may be applied to deflection type systems and ink on demand systems is to vibrate and heat the nozzle. However, none of these arrangements are entirely effective.
Other expedients to prevent nozzle clogs include vibrating the nozzle weakly when the printer is not in actual operation, placing a cap on the nozzle and filling it with solvent and circulating solvent through the nozzle when the printer is not in operation. Although these systems are applicable to both deflection type and demand type printing apparatus, they are incapable of preventing ink clogs caused by introduction of dirt when replacing a filter, maintenance of a pressure regulator valve, solidification of ink during a long period of non-use, introduction of fine dust particles through the nozzle and the like. Merely increasing the ink pressure cannot clear a serious clog and imposes a strain on the nozzle and piping.